fix type information lost from nested decoder types, closes #479

CHANGELOG.md

@@ -14,6 +14,13 @@
 **Note**: Gaps between patch versions are faulty/broken releases.
 **Note**: A feature tagged as Experimental is in a high state of flux, you're at risk of it changing without notice.
 
+# 2.2.5
+
+- **Experimental**
+  - fix type information lost from nested decoder types, #479 (@gcanti)
+  - `JsonEncoder`
+    - change `id` signature (@gcanti)
+
 # 2.2.4
 
 - **Polish**

docs/modules/Decoder.ts.md

@@ -298,7 +298,9 @@ Added in v2.2.0
 **Signature**
 
 ```ts
-export declare function partial<A>(properties: { [K in keyof A]: Decoder<A[K]> }): Decoder<Partial<A>>
+export declare function partial<A>(
+  properties: { [K in keyof A]: Decoder<A[K]> }
+): Decoder<Partial<{ [K in keyof A]: A[K] }>>
 ```
 
 Added in v2.2.0
@@ -399,7 +401,7 @@ Added in v2.2.0
 **Signature**
 
 ```ts
-export declare function type<A>(properties: { [K in keyof A]: Decoder<A[K]> }): Decoder<A>
+export declare function type<A>(properties: { [K in keyof A]: Decoder<A[K]> }): Decoder<{ [K in keyof A]: A[K] }>
 ```
 
 Added in v2.2.0

docs/modules/Eq.ts.md

@@ -137,7 +137,7 @@ Added in v2.2.2
 **Signature**
 
 ```ts
-export declare function partial<A>(properties: { [K in keyof A]: Eq<A[K]> }): Eq<Partial<A>>
+export declare function partial<A>(properties: { [K in keyof A]: Eq<A[K]> }): Eq<Partial<{ [K in keyof A]: A[K] }>>
 ```
 
 Added in v2.2.2
@@ -197,7 +197,7 @@ Added in v2.2.2
 **Signature**
 
 ```ts
-export declare const type: <A>(eqs: { [K in keyof A]: E.Eq<A[K]> }) => E.Eq<A>
+export declare const type: <A>(eqs: { [K in keyof A]: E.Eq<A[K]> }) => E.Eq<{ [K in keyof A]: A[K] }>
 ```
 
 Added in v2.2.2

docs/modules/Guard.ts.md

@@ -185,7 +185,9 @@ Added in v2.2.0
 **Signature**
 
 ```ts
-export declare function partial<A>(properties: { [K in keyof A]: Guard<A[K]> }): Guard<Partial<A>>
+export declare function partial<A>(
+  properties: { [K in keyof A]: Guard<A[K]> }
+): Guard<Partial<{ [K in keyof A]: A[K] }>>
 ```
 
 Added in v2.2.0
@@ -262,7 +264,7 @@ Added in v2.2.0
 **Signature**
 
 ```ts
-export declare function type<A>(properties: { [K in keyof A]: Guard<A[K]> }): Guard<A>
+export declare function type<A>(properties: { [K in keyof A]: Guard<A[K]> }): Guard<{ [K in keyof A]: A[K] }>
 ```
 
 Added in v2.2.0

docs/modules/JsonCodec.ts.md

@@ -188,7 +188,9 @@ Added in v2.2.3
 **Signature**
 
 ```ts
-export declare const partial: <A>(properties: { [K in keyof A]: JsonCodec<A[K]> }) => JsonCodec<Partial<A>>
+export declare const partial: <A>(
+  properties: { [K in keyof A]: JsonCodec<A[K]> }
+) => JsonCodec<Partial<{ [K in keyof A]: A[K] }>>
 ```
 
 Added in v2.2.3
@@ -266,7 +268,7 @@ Added in v2.2.3
 **Signature**
 
 ```ts
-export declare const type: <A>(properties: { [K in keyof A]: JsonCodec<A[K]> }) => JsonCodec<A>
+export declare const type: <A>(properties: { [K in keyof A]: JsonCodec<A[K]> }) => JsonCodec<{ [K in keyof A]: A[K] }>
 ```
 
 Added in v2.2.3

docs/modules/JsonEncoder.ts.md

@@ -142,10 +142,10 @@ Added in v2.2.3
 **Signature**
 
 ```ts
-export declare const id: JsonEncoder<Json>
+export declare function id<A extends Json>(): JsonEncoder<A>
 ```
 
-Added in v2.2.3
+Added in v2.2.5
 
 # intersection
 
@@ -182,7 +182,9 @@ Added in v2.2.3
 **Signature**
 
 ```ts
-export declare const partial: <A>(properties: { [K in keyof A]: JsonEncoder<A[K]> }) => JsonEncoder<Partial<A>>
+export declare const partial: <A>(
+  properties: { [K in keyof A]: JsonEncoder<A[K]> }
+) => JsonEncoder<Partial<{ [K in keyof A]: A[K] }>>
 ```
 
 Added in v2.2.3
@@ -236,7 +238,9 @@ Added in v2.2.3
 **Signature**
 
 ```ts
-export declare const type: <A>(properties: { [K in keyof A]: JsonEncoder<A[K]> }) => JsonEncoder<A>
+export declare const type: <A>(
+  properties: { [K in keyof A]: JsonEncoder<A[K]> }
+) => JsonEncoder<{ [K in keyof A]: A[K] }>
 ```
 
 Added in v2.2.3

docs/modules/Schemable.ts.md

@@ -37,8 +37,8 @@ export interface Schemable<S> {
   readonly number: HKT<S, number>
   readonly boolean: HKT<S, boolean>
   readonly nullable: <A>(or: HKT<S, A>) => HKT<S, null | A>
-  readonly type: <A>(properties: { [K in keyof A]: HKT<S, A[K]> }) => HKT<S, A>
-  readonly partial: <A>(properties: { [K in keyof A]: HKT<S, A[K]> }) => HKT<S, Partial<A>>
+  readonly type: <A>(properties: { [K in keyof A]: HKT<S, A[K]> }) => HKT<S, { [K in keyof A]: A[K] }>
+  readonly partial: <A>(properties: { [K in keyof A]: HKT<S, A[K]> }) => HKT<S, Partial<{ [K in keyof A]: A[K] }>>
   readonly record: <A>(codomain: HKT<S, A>) => HKT<S, Record<string, A>>
   readonly array: <A>(items: HKT<S, A>) => HKT<S, Array<A>>
   readonly tuple: <A extends ReadonlyArray<unknown>>(...components: { [K in keyof A]: HKT<S, A[K]> }) => HKT<S, A>
@@ -62,8 +62,8 @@ export interface Schemable1<S extends URIS> {
   readonly number: Kind<S, number>
   readonly boolean: Kind<S, boolean>
   readonly nullable: <A>(or: Kind<S, A>) => Kind<S, null | A>
-  readonly type: <A>(properties: { [K in keyof A]: Kind<S, A[K]> }) => Kind<S, A>
-  readonly partial: <A>(properties: { [K in keyof A]: Kind<S, A[K]> }) => Kind<S, Partial<A>>
+  readonly type: <A>(properties: { [K in keyof A]: Kind<S, A[K]> }) => Kind<S, { [K in keyof A]: A[K] }>
+  readonly partial: <A>(properties: { [K in keyof A]: Kind<S, A[K]> }) => Kind<S, Partial<{ [K in keyof A]: A[K] }>>
   readonly record: <A>(codomain: Kind<S, A>) => Kind<S, Record<string, A>>
   readonly array: <A>(items: Kind<S, A>) => Kind<S, Array<A>>
   readonly tuple: <A extends ReadonlyArray<unknown>>(...components: { [K in keyof A]: Kind<S, A[K]> }) => Kind<S, A>

docs/modules/Type.ts.md

@@ -161,7 +161,7 @@ Added in v2.2.3
 **Signature**
 
 ```ts
-export declare function partial<A>(properties: { [K in keyof A]: Type<A[K]> }): Type<Partial<A>>
+export declare function partial<A>(properties: { [K in keyof A]: Type<A[K]> }): Type<Partial<{ [K in keyof A]: A[K] }>>
 ```
 
 Added in v2.2.3
@@ -238,7 +238,7 @@ Added in v2.2.3
 **Signature**
 
 ```ts
-export declare function type<A>(properties: { [K in keyof A]: Type<A[K]> }): Type<A>
+export declare function type<A>(properties: { [K in keyof A]: Type<A[K]> }): Type<{ [K in keyof A]: A[K] }>
 ```
 
 Added in v2.2.3

dtslint/ts3.5/Codec.ts

@@ -0,0 +1,17 @@
+import * as _ from '../../src/Codec'
+
+// $ExpectType Codec<{ a: string; b: { c: number; }; }, { a: string; b: { c: number; }; }>
+_.type({
+  a: _.string,
+  b: _.type({
+    c: _.number
+  })
+})
+
+// $ExpectType Codec<Partial<{ a: string; b: Partial<{ c: number; }>; }>, Partial<{ a: string; b: Partial<{ c: number; }>; }>>
+_.partial({
+  a: _.string,
+  b: _.partial({
+    c: _.number
+  })
+})

dtslint/ts3.5/Decoder.ts

@@ -0,0 +1,17 @@
+import * as _ from '../../src/Decoder'
+
+// $ExpectType Decoder<{ a: string; b: { c: number; }; }>
+_.type({
+  a: _.string,
+  b: _.type({
+    c: _.number
+  })
+})
+
+// $ExpectType Decoder<Partial<{ a: string; b: Partial<{ c: number; }>; }>>
+_.partial({
+  a: _.string,
+  b: _.partial({
+    c: _.number
+  })
+})

dtslint/ts3.5/Econder.ts → dtslint/ts3.5/Encoder.ts

@@ -1,5 +1,4 @@
 import * as E from '../../src/Encoder'
-import { identity } from 'fp-ts/lib/function'
 
 const NumberToString: E.Encoder<string, number> = {
   encode: String
@@ -9,17 +8,17 @@ const BooleanToNumber: E.Encoder<number, boolean> = {
   encode: (b) => (b ? 1 : 0)
 }
 
-export const Person = E.type({ name: E.categoryEncoder.id<string>(), age: NumberToString })
+export const OfTest = E.type({ a: E.id<string>(), b: E.type({ c: NumberToString }) })
 
 //
 // TypeOf
 //
-export type Person = E.TypeOf<typeof Person> // $ExpectType { name: string; age: number; }
+export type OfTest = E.TypeOf<typeof OfTest> // $ExpectType { a: string; b: { c: number; }; }
 
 //
 // OutputOf
 //
-export type PersonOut = E.OutputOf<typeof Person> // $ExpectType { name: string; age: string; }
+export type OfTestOutput = E.OutputOf<typeof OfTest> // $ExpectType { a: string; b: { c: string; }; }
 
 //
 // nullable
@@ -29,12 +28,12 @@ E.nullable(NumberToString) // $ExpectType Encoder<string | null, number | null>
 //
 // type
 //
-E.type({ a: NumberToString }) // $ExpectType Encoder<{ a: string; }, { a: number; }>
+E.type({ a: E.type({ b: NumberToString }) }) // $ExpectType Encoder<{ a: { b: string; }; }, { a: { b: number; }; }>
 
 //
 // partial
 //
-E.partial({ a: NumberToString }) // $ExpectType Encoder<Partial<{ a: string; }>, Partial<{ a: number; }>>
+E.partial({ a: E.partial({ b: NumberToString }) }) // $ExpectType Encoder<Partial<{ a: Partial<{ b: string; }>; }>, Partial<{ a: Partial<{ b: number; }>; }>>
 
 //
 // record

dtslint/ts3.5/Eq.ts

@@ -0,0 +1,17 @@
+import * as _ from '../../src/Eq'
+
+// $ExpectType Eq<{ a: string; b: { c: number; }; }>
+_.type({
+  a: _.string,
+  b: _.type({
+    c: _.number
+  })
+})
+
+// $ExpectType Eq<Partial<{ a: string; b: Partial<{ c: number; }>; }>>
+_.partial({
+  a: _.string,
+  b: _.partial({
+    c: _.number
+  })
+})

dtslint/ts3.5/Guard.ts

@@ -0,0 +1,17 @@
+import * as _ from '../../src/Guard'
+
+// $ExpectType Guard<{ a: string; b: { c: number; }; }>
+_.type({
+  a: _.string,
+  b: _.type({
+    c: _.number
+  })
+})
+
+// $ExpectType Guard<Partial<{ a: string; b: Partial<{ c: number; }>; }>>
+_.partial({
+  a: _.string,
+  b: _.partial({
+    c: _.number
+  })
+})

dtslint/ts3.5/JsonCodec.ts

@@ -0,0 +1,17 @@
+import * as _ from '../../src/JsonCodec'
+
+// $ExpectType JsonCodec<{ a: string; b: { c: number; }; }>
+_.type({
+  a: _.string,
+  b: _.type({
+    c: _.number
+  })
+})
+
+// $ExpectType JsonCodec<Partial<{ a: string; b: Partial<{ c: number; }>; }>>
+_.partial({
+  a: _.string,
+  b: _.partial({
+    c: _.number
+  })
+})

dtslint/ts3.5/JsonEncoder.ts

@@ -0,0 +1,17 @@
+import * as _ from '../../src/JsonEncoder'
+
+// $ExpectType JsonEncoder<{ a: string; b: { c: number; }; }>
+_.type({
+  a: _.id<string>(),
+  b: _.type({
+    c: _.id<number>()
+  })
+})
+
+// $ExpectType JsonEncoder<Partial<{ a: string; b: Partial<{ c: number; }>; }>>
+_.partial({
+  a: _.id<string>(),
+  b: _.partial({
+    c: _.id<number>()
+  })
+})

dtslint/ts3.5/Schema.ts

@@ -1,4 +1,3 @@
-import * as D from '../../src/Decoder'
 import { Schemable, WithUnknownContainers, memoize, WithRefinement, WithUnion } from '../../src/Schemable'
 import { HKT } from 'fp-ts/lib/HKT'
 
@@ -15,8 +14,8 @@ function make<A>(f: Schema<A>): Schema<A> {
 //
 // TypeOf
 //
-export const Person = make((S) => S.type({ name: S.string, age: S.number }))
-export type Person = TypeOf<typeof Person> // $ExpectType { name: string; age: number; }
+export const OfTest = make((S) => S.type({ a: S.string, b: S.type({ c: S.number }) }))
+export type OfTest = TypeOf<typeof OfTest> // $ExpectType { a: string; b: { c: number; }; }
 
 //
 // literal
@@ -46,12 +45,12 @@ make((S) => S.nullable(S.string)) // $ExpectType Schema<string | null>
 //
 // type
 //
-make((S) => S.type({ a: S.string })) // $ExpectType Schema<{ a: string; }>
+make((S) => S.type({ a: S.string, b: S.type({ c: S.number }) })) // $ExpectType Schema<{ a: string; b: { c: number; }; }>
 
 //
 // partial
 //
-make((S) => S.partial({ a: S.string })) // $ExpectType Schema<Partial<{ a: string; }>>
+make((S) => S.partial({ a: S.string, b: S.partial({ c: S.number }) })) // $ExpectType Schema<Partial<{ a: string; b: Partial<{ c: number; }>; }>>
 
 //
 // record

dtslint/ts3.5/Type.ts

@@ -0,0 +1,17 @@
+import * as _ from '../../src/Type'
+
+// $ExpectType Type<{ a: string; b: { c: number; }; }>
+_.type({
+  a: _.string,
+  b: _.type({
+    c: _.number
+  })
+})
+
+// $ExpectType Type<Partial<{ a: string; b: Partial<{ c: number; }>; }>>
+_.partial({
+  a: _.string,
+  b: _.partial({
+    c: _.number
+  })
+})

package.json

@@ -1,6 +1,6 @@
 {
   "name": "io-ts",
-  "version": "2.2.4",
+  "version": "2.2.5",
   "description": "TypeScript runtime type system for IO decoding/encoding",
   "files": [
     "lib",

src/Codec.ts

@@ -139,7 +139,9 @@ export function type<P extends Record<string, Codec<any, any>>>(
 export function partial<P extends Record<string, Codec<any, any>>>(
   properties: P
 ): Codec<Partial<{ [K in keyof P]: OutputOf<P[K]> }>, Partial<{ [K in keyof P]: TypeOf<P[K]> }>> {
-  return make(D.partial(properties), E.partial(properties))
+  // these tow `any`s are required to make typescript@3.5 compile
+  //                               vvvvvv                          vvvvvv
+  return make(D.partial(properties as any), E.partial(properties)) as any
 }
 
 /**